1. Technical Field
The present invention relates, for example, to a light guide device that guides video image light to present a viewer with video images formed, for example, by an image display device, and particularly to a light guide device suitable for a head-mounted display worn around the viewer's head, a virtual image display apparatus using the light guide device, and a method for manufacturing the light guide device.
2. Related Art
A variety of optical systems incorporated in a virtual image display apparatus, such as a head-mounted display (hereinafter also referred to as HMD) worn around a viewer's head, have been proposed (see JP-A-2013-73187, for example).
In a virtual image display apparatus of this type, to guide image light in an appropriate state, it is necessary to keep a satisfactory state of a surface portion of a light guide plate that allows propagation of the image light through reflection or any other optical phenomenon. It is therefore conceivable to provide a hard coat layer to prevent damage to the surface portion and allow dirt on the surface to be readily removed. For example, to superimpose the image light (video image light) and outside light on each other, a see-through-type optical system has been proposed (see JP-A-2013-73187, for example). In a see-through-type HMD of this type, it is important to provide a hard coat that substantially prevents scratches and dirt on the light guide plate or any other light guide portion that is handled as an exterior part.
The light guide plate or any other light guide portion, however, typically has a complicated shape in many cases, and fully coating the light guide portion is not always readily performed. For example, when the light guide plate is formed of a plurality of complicated curved surfaces, it is conceivable that a coating liquid solution undesirably flows in such a way that it converges to a single point of the light guide portion in a coating process, resulting in a large amount of liquid drooping on the surface or hard coat failure. Further, for example, in a coating process using dipping operation, presence of a stepped surface substantially perpendicular to the lift-up direction in the dipping operation conceivably causes the coat liquid solution to build up on the stepped surface, resulting in liquid drooping. In particular, a stepped portion tends to be formed between a plurality of surfaces that form a light guide portion, and it is not always easy in this case to prevent the coating liquid from drooping but appropriately form a hard coat layer.